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Recycled polyethylene-terephthalate (rPET) nanocomposites of reduced flammability were prepared by combining aluminum-alkylphosphinate (AlPi) flame retardant (FR) and natural montmorillonite (MMT), in order to demonstrate that durable, technical products can be produced from recycled materials. During the development of the material, by varying the FR content, the ratio and the type of MMTs, rheological, morphological, mechanical and flammability properties of the nanocomposites were comprehensively investigated. Related to the differences between the dispersion and nucleation effect of MMT and organo-modified MMT (oMMT) in rPET matrix, analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and Differential Scanning Calorimetry (DSC), mechanical properties of the nanocomposites changed differently. The flexural strength and modulus were increased more significantly by adding untreated MMT than by the oMMT, however the impact strength was decreased by both types of nanofillers. The use of different type of MMTs resulted in contradictory flammability test result; time-to-ignition (TTI) during cone calorimeter tests decreased when oMMT was added to the rPET, however MMT addition resulted in an increase of the TTI also when combined with 4% FR. The limiting oxygen index (LOI) of the oMMT containing composites decreased independently from the FR content, however, the MMT increased it noticeably. V0 classification according to the UL-94 standard was achieved with as low as 4% FR and 1% MMT content. The applicability of the upgraded recycled material was proved by a pilot experiment, where large-scale electronic parts were produced by injection molding and characterized with respect to the commercially available counterparts.

Recycled polyethylene-terephthalate (RPET) bottle regrinds were physically foamed after two types of industrially feasible molecular weight increasing processes. Intrinsic viscosity (IV) of initial waste (0.71 dl/g) increased both after reactive extrusion carried out using a multifunctional epoxy-based chain extender (0.74 dl/g) and after solid state polycondensation (SSP) (0.78 dl/g), while capillary rheometry revealed higher degree of branching in the chain extended PET material. Despite the relatively low IV values (below 0.80 dl/g), physical foaming, a mild and cost efficient way, was successful in both cases, uniform microcellular foam structures with void fractions ranging between 75 and 83% were achieved. During the experiments morphology change in the materials was tracked by differential scanning calorimetry (DSC) besides recording IV values. The IV drop during foaming was between 0.03-0.10 depending on the pre-processing technology. Structure of 2 foams produced from the two different modified RPET materials was compared with each other based on scanning electron microscopic imaging (SEM) of cryogenic fracture surfaces.The average cell diameters were measured to be 213 and 360 µm in the case of chain extended and SSP-modified materials, respectively.

Foam injection molded samples were produced from recycled polyethylene-terephthalate using endothermic and exothermic foaming agents at different mold temperatures. The foam structure was analyzed by computer tomography and optical microscopy. The morphological properties of samples were analyzed by differential scanning calorimetry, using the three-phase model. Viscosities of the melts were changed during processing by endothermic and exothermic foaming agents, and as a result different foam structures were formed. Relationships between mold temperature and porosity were found. Morphologies of the samples made with different foaming agents were different, also due to the different cooling rates caused by the endothermic and exothermic foaming reactions.